In recent years, as a digitization technology has been developed, image data and text data of a newspaper, a magazine, and the like can be provided as electronic data. The contents of such a kind of electronic data are generally read by being displayed on a display device included in a television, a personal computer, a portable electronic terminal, or the like.
Display media such as a liquid crystal display device are very different form paper media such as a newspaper and a magazine. One of features of display media is that pages are switched on a screen of a display device, which is very different from the way paper media usually are handled. Such a difference in the way they are handled causes the display media a problem such as a lower visible efficiency in text reading, sentence comprehension, or image recognition than the paper media.
It is important for display media such as a liquid crystal display device to increase in visible efficiency and to reduce in power consumption in order to be conveniently used. As a countermeasure, a technique is disclosed in which power consumption is decreased by reduction in refresh rate, that is, the number of times of rewriting an image data (see Patent Document 1).